Video signal format converter

1. A video signal converter for converting a number of scanning lines of a first input video signal into a different number of scanning lines of a second video signal, the video signal converter comprising: (a) phase-locked-loop means which receives a horizontal pulse synchronized with said first input video signal, and generates a first clock signal synchronized with the horizontal pulse, (b) an Analog-to-Digital converter which converts said first input video signal using said first clock signal, (c) video converting means which receives (1) a first digital video signal tapped off from said Analog-to-Digital converter, (2) said first clock signal, (3) said horizontal pulse and (4) a vertical pulse synchronized with said first video signal, and converts a number of scanning lines of said first digital video signal into a number of scanning lines of a second digital video signal, (d) a clock signal generator which outputs a second clock signal independent of said first clock signal, (e) a memory which stores said second digital video signal tapped off from said video converting means by using said first clock signal from said phase-locked-loop means, and reads out said second digital video signal by using said second clock signal from said clock signal generator before outputting a third digital video signal, and (f) a Digital-to-Analog converter which converts, the third digital video signal tapped off from the memory into analog format from digital format, whereby said number of scanning lines of the inputted first video signal is converted, and then the second video signal having converted scanning lines is outputted, and said phase-locked-loop means generates the first clock signal so that a number of effective horizontal pixels of the inputted first video signal equals that of the outputted second video signal.

2. A video signal converter for converting a number of scanning lines of a first input video signal into a different number of scanning lines of a second video signal, the video signal converter comprising: (a) phase-locked-loop means which receives a horizontal pulse synchronized with said first input video signal, and generates a first clock signal synchronized with the horizontal pulse, (b) an Analog-to-Digital converter which converts said first input video signal using said first clock signal, (c) video converting means which receives (1) a first digital video signal tapped off from said Analog-to-Digital converter, (2) said first clock signal, (3) said horizontal pulse and (4) a vertical pulse synchronized with said first video signal, and converts a number of scanning lines of said first digital video signal into a number of scanning lines of a second digital video signal, (d) a clock signal generator which outputs a second clock signal independent of said first clock signal, (e) a memory which stores said second digital video signal tapped off from said video converting means by using said first clock signal from said phase-locked-loop means, and reads out said second digital video signal by using said second clock signal from said clock signal generator before outputting a third digital video signal, (f) a Digital-to-Analog converter which converts, the third digital video signal tapped off from the memory into analog format from digital format, (g) counter means which is triggered by the first clock signal and synchronized with the inputted horizontal pulse, and (h) masking means which provides a masking process to an interval of said horizontal pulse by using said counter means, whereby said number of scanning lines of the inputted first video signal is converted, and then the second video signal having converted scanning lines is outputted.

3. The video signal converter as defined in claim 2, further comprising mask position determination means for determining a starting position of masking by referring to a position of the horizontal pulse.

4. The video signal converter as defined in claim 2, wherein said counter means, which is triggered by the first clock signal, counts a horizontal frequency, and identifies the horizontal frequency of the first video signal by comparing a predetermined threshold frequency with the counted frequency, thereby controlling said phase-locked-loop means.

5. The video signal converter as defined in claim 2, wherein said counter means, which is triggered by the first clock signal and synchronized with a second horizontal pulse undergone the masking process, counts a horizontal frequency, and identifies a horizontal frequency of the first video signal by comparing a predetermined threshold frequency with the counted frequency, thereby controlling said phase-locked-loop means.

6. The video signal converter as defined in claim 2, further comprising second counter means, which is triggered by the second clock signal and synchronized with a second horizontal pulse undergone the masking process, counts a horizontal frequency, and identifies a horizontal frequency of the first video signal by comparing a predetermined threshold frequency with the counted frequency, thereby controlling said phase-locked-loop means.

7. The video signal converter as defined in claim 6, further comprising hue conversion means for converting a hue of an image corresponding to said first input video signal, wherein, said hue is converted in step with a conversion of the first video signal into the second video signal.

8. The video signal converter as defined in claim 7, wherein said hue conversion means is appropriately switched responsive to the identification of the horizontal frequency of the horizontal pulse.

9. The video signal converter as defined in claim 6, further comprising contour correction means which switches contour correction of an image corresponding to said first input video signal along at least one of a horizontal direction and a vertical direction responsive to the identification of the horizontal frequency of the horizontal pulse.

10. The video signal converter as defined in claim 6, further comprising mask control means which disables the masking process to the horizontal pulse responsive to a power supply being activated.

11. The video signal converter as defined in claim 6, further comprising channel-change-detection-means which disables the masking process to the horizontal pulse responsive to a channel being changed during receiving of broadcasting.

12. A video signal converter for converting a number of scanning lines of a first input video signal into a different number of scanning lines of a second video signal, the video signal converter comprising: (a) phase-locked-loop means which receives a horizontal pulse synchronized with said first input video signal, and generates a first clock signal synchronized with the horizontal pulse, (b) an Analog-to-Digital converter which converts said first input video signal using said first clock signal, (c) video converting means which receives (1) a first digital video signal tapped off from said Analog-to-Digital converter, (2) said first clock signal, (3) said horizontal pulse and (4) a vertical pulse synchronized with said first video signal, and converts a number of scanning lines of said first digital video signal into a number of scanning lines of a second digital video signal, (d) a clock signal generator which outputs a second clock signal independent of said first clock signal, (e) a memory which stores said second digital video signal tapped off from said video converting means by using said first clock signal from said phase-locked-loop means, and reads out said second digital video signal by using said second clock signal from said clock signal generator before outputting a third digital video signal, and (f) a Digital-to-Analog converter which converts, the third digital video signal tapped off from the memory into analog format from digital format, whereby said number of scanning lines of the inputted first video signal is converted, and then the second video signal having a converted scanning lines is outputted, and the first video signal is fed into the Analog-to-Digital converter through a low pass filter.

13. The video signal converter as defined in claim 4, wherein the first video signal is fed into the Analog-to-Digital converter through a low pass filter, while a characteristic of said low pass filter is controlled by a counting result of the horizontal frequency of the first video signal .